A fly’s paradise: Near a giant hog factory in North Carolina, downed pigs fester while sprayers spread untreated manure onto fields. Photo: Steve WingWhat sort of antibiotic-resistant pathogens are growing on factory farms, along with all the cheap pork chops and chicken wings? And what level of threat do they pose to our health?

Well, we know that in total, factory-farm animals consume a jaw-dropping four times as many antibiotics as do people in the United States, thanks to diligent reporting by Maryn McKenna and Ralph Loglisci and work by Rep. Louise Slaughter (D-N.Y.).

And we know that a kind of antibiotic-resistant staph infection called MRSA now kills more people than AIDS — and infects people who never set foot in a hospital, which is the site where MRSA is thought to have originated. We also know, due to the stellar work of Iowa State University researcher Tara Smith, that pigs in confined animal feedlot operations, and the workers who tend them, routinely carry MRSA strains (her paper can be found here).

And now we know of yet another means by which antibiotic-resistant nasties can make their way from meat factories into the broader community: through the cockroaches and flies drawn to the titanic amounts of manure produced on factory farms. For a paper published last month in the journal Microbiology, researchers from North Carolina State and Kansas State universities took one for the team — i.e., the public. They did something few of us would want to do: rounded up common flies and roaches hanging around factory hog farms, and tested them to see what kinds of bacteria they were harboring.

Their finding? More than 90 percent of the insects sampled carried forms of the bacteria Enterococci that are resistant to at least one common antibiotic, and often more than one. Here’s how the authors summed up their findings in the paper’s abstract:

This study shows that house flies and German [common] cockroaches in the confined swine production environment likely serve as vectors and/or reservoirs of antibiotic resistant and potentially virulent enterococci and consequently may play an important role in animal and public health.

In a press release, study coauthor Coby Schal, entomology professor at NC State, broke it down in simpler terms:

The big concern is not that humans will acquire drug-resistant bacteria from their properly cooked bacon or sausage, but rather that the bacteria will be transferred to humans from the common pests that live with pigs and then move in with us.

Meanwhile, evidence is mounting that factory-scale animal farms exact a high toll from the people who live around them in other ways, too. A study by University of North Carolina professor Steve Wing and others shows that people with the bad luck to live near giant hog farms suffer demonstrably worse health when the factories are getting up to malodorous stuff like spraying untreated (and thus antibiotic-resistant-bacteria-laden) manure on fields. Among the many hidden costs of cheap pork is that people who live near factory farms are doomed either to be sick or shut in at certain times of the year. (McKenna has an excellent discussion of the Wing study on her Wired blog.)

To answer the questions I posed in the opening paragraph, it seems we’re brewing up some pretty nasty pathogens in our meat factories, along with all the pork chops and chicken wings. And they’re coming our way, carried out on the meat itself, by factory-farm workers, and by common creepy-crawly and flying insects.

Seems like there should be a law banning the non-therapeutic use of antibiotics on farms. In 2009, Rep. Louise Slaughter introduced the Preservation of Antibiotics for Medical Treatment Act (PAMTA). So far, the meat industry has managed to, well, slaughter it. But she plans to introduce PAMTA again this year.